Image forming apparatus

Abstract

An image forming apparatus includes a head tank and a main tank that sends liquid to the head tank. When the remaining ink amount in the main tank is less than or equal to a predetermined amount (near empty), the liquid sending amount to be sent from the main tank to the head tank required for detecting a full state of the head tank is set to be a second liquid sending amount which is greater than a usual first liquid sending amount. An ink supply operation is performed to send liquid corresponding to the second liquid sending amount, from the main tank to the head tank. Then, it is determined whether the head tank is in a full state. When the head tank is not in a full state, the main tank is determined to be in an ink empty state.

What is claimed is: 
     
       1. An image forming apparatus comprising:
 a recording head configured to jet liquid droplets; 
 a head tank configured to accommodate liquid to be supplied to the recording head; 
 a main tank configured to accommodate liquid to be supplied to the head tank; 
 a liquid sending pump configured to send the liquid from the main tank to the head tank; 
 a full tank detection unit configured to detect whether the head tank is in a full state when sending liquid from the main tank to the head tank; 
 an empty determination unit configured to determine an empty state of the main tank, when the full state of the head tank is not detected by the full tank detection unit even if a predetermined liquid sending amount is sent from the main tank to the head tank; and 
 a near empty detection unit configured to detect whether a remaining liquid amount in the main tank is less than or equal to a predetermined remaining amount, wherein 
 the full tank detection unit switches the predetermined liquid sending amount to be sent from the main tank to the head tank, which is required for detecting whether the head tank is in the full state, between a first liquid sending amount and a second liquid sending amount that is greater than the first liquid sending amount, wherein 
 the full tank detection unit detects whether the head tank is in the full state based on a liquid sending operation of sending the first liquid sending amount, when the remaining liquid amount in the main tank is greater than the predetermined remaining amount, and 
 the full tank detection unit detects whether the head tank is in the full state based on a liquid sending operation of sending the second liquid sending amount, when the remaining liquid amount in the main tank is less than or equal to the predetermined remaining amount. 
 
     
     
       2. The image forming apparatus according to  claim 1 , wherein
 the full tank detection unit detects whether the head tank is in the full state based on the liquid sending operation of sending the second liquid sending amount, when a liquid sending interval between liquid sending operations of sending the liquid from the main tank to the head tank is greater than or equal to a predetermined time period. 
 
     
     
       3. The image forming apparatus according to  claim 1 , wherein
 the liquid sending pump is a reversible pump through which the liquid can be sent in a reverse direction from the head tank to the main tank, wherein 
 when the full tank detection unit detects that the head tank is in the full state based on the liquid sending operation of sending the second liquid sending amount, a difference liquid amount is sent in the reverse direction from the head tank to the main tank, the difference liquid amount corresponding to a difference between the first liquid sending amount and the second liquid sending amount.